Alzheimer's disease and dementia are diseases which result in a progressive deterioration of neurons in the brain which causes cognitive deterioration and changes in behavior. With Alzheimer's disease, there is loss of short-term memory and minor forgetfulness which becomes greater as the illness progresses to major memory loss with a relative preservation of older memories. As the disease progresses even further, there is cognitive or intellectual impairment which extends to language degeneration (having difficulty remembering words to being completely unable to speak, read, or write), loss of the ability to execute or carry out learned purposeful movements, and a loss of ability to recognize objects, persons, sounds, shapes, or smells.
Neurons are cells which transmit information via synapses. Neurons connect to each other to form neural networks. Neurons are electrically excitable cells which transmit information by electrical and chemical signaling by synapses which establish connections with other neuron cells. With the progression of Alzheimer's disease and other neurodegenerative diseases, the connectivity of the neurons are adversely affected, such as by the generation of plaque and abnormal proteins called tau proteins.